[evlatests] Test data from Tuesday

[Bryan Butler]

were the irregular amplitudes observed?  the few seconds, 5%-ish ones?

	-bryan


Rick Perley wrote, On 9/2/09 10:48:
>     Michael took one hour of L-band data on 3C286, and a 'blank' field 5 
> degrees south, on Tuesday afternoon.  
> 
>     Most of the problems noted earlier remain with us:
> 
>     1) sub-band shapes for 8 LCP, all subands remain crazy -- no longer 
> a single sinusoid.  Looks like about 12 cycles. 
>     2) 3LCP, subbands 3 and 4 remain sloped, with near zero sensitivity 
> at the boundary. 
>     3) A huge number of identical zero visibilities noted -- the usual 
> 0.1% randomly placed, plus a large fraction of antenna-based zeros.  
> However, all of these are associated with antennas 3, 4, 8 and 23, and 
> only for the first ~7 minutes of so.  After that, all is normal -- 
> *except* for 23 LCP, which is identically zero for all subbands 
> throughout the entire run. 
>     4) We are getting steps in gain, always associated with scan 
> boundaries, and (with one exception) only on the LCP side.  All these 
> gain changes are of the 1-db variety.  Antennas affected are 4, 24 and 
> 25.  The single exception is 25RCP -- this has 4 gain changes over the 
> run, none of them of the 1 dB type.  I recall having noted this before, 
> last month. 
>     5) Delays are the same as at C-band (plus/minus a couple of nsec). 
> 
>     Despite these issues, the data calibrate beautifully after 
> flagging.   Most bandpasses are stable (there are exceptions that I'll 
> note, this afternoon).  The famous VLA suckout near 1465 MHz is 
> completely absent on antenna 24 -- as it should be. 
> 
>     Decent images have been made -- I'll return to this in the afternoon. 
> 
>     Michael's attempt to observe a noise field almost succeeded, but he 
> failed to note that the calibrator 3C287 is located 5 degrees south of 
> 3C286!    But this little accident is actually good -- a full-field 
> image of the 'blank' field shows a nice response of 3C287, 30 arcminutes 
> from the randomly-chosen phase center -- i.e. near the first null. 
> 
>    
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